Such a system is conventionally known, for example, from Japanese Patent Application Laid-open No.6-221125, Japanese Utility Model Application Laid-open No.7-8508 and the like.
In the above-identified known systems, to fix the support shafts to the rocker arms, the support shafts or the rocker arms are caulked or staked at a plurality of circumferential points at opposite ends of the support shafts. However, it is common that the support shafts and the rocker arms are subjected to a thermal treatment in order to increase the hardness thereof, and in carrying out the caulking or staking, it is necessary to partially remove the thermal treated portions from the support shafts or the rocker arms which have been subjected to the thermal treatment, resulting in a complicated operation for fixing the support shafts to the rocker arms, in cooperation with the fact that the caulking or staking must be carried out at the plurality of circumferential points.
The present invention has been accomplished with such circumstance in view, and it is an object of the present invention to provide a valve operating system in an internal combustion engine, wherein the support shafts can be easily fixed to the rocker arms.